'\"macro stdmacro
.\"
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.\" Copyright (c) 2007 Aconex, Inc.  All Rights Reserved.
.\"
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.\" under the terms of the GNU General Public License as published by the
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.TH PMPARSEHOSTSPEC 3 "PCP" "Performance Co-Pilot"
.SH NAME
\f3__pmParseHostSpec\f1,
\f3__pmUnparseHostSpec\f1,
\f3__pmFreeHostSpec\f1 \- uniform host specification parser
.SH "C SYNOPSIS"
.ft 3
#include "pmapi.h"
.br
#include "libpcp.h"
.sp
.ad l
.hy 0
.in +8n
.ti -8n
int __pmParseHostSpec(const char *\fIstring\fP, pmHostSpec **\fIhostsp\fP, int\ *\fIcount\fP, char\ **\fIerrmsg\fP);
.br
.ti -8n
int __pmUnparseHostSpec(pmHostSpec *\fIhosts\fP, int \fIcount\fP, char *\fIstring\fP, size_t \fIsize\fP);
.br
.ti -8n
void __pmFreeHostSpec(pmHostSpec *\fIhosts\fP, int \fIcount\fP);
.sp
.in
.hy
.ad
cc ... \-lpcp
.ft 1
.SH CAVEAT
This documentation is intended for internal Performance Co-Pilot
(PCP) developer use.
.PP
These interfaces are not part of the PCP APIs that are guaranteed to
remain fixed across releases, and they may not work, or may provide
different semantics at some point in the future.
.SH DESCRIPTION
.B __pmParseHostSpec
accepts a
.B string
specifying the location of a PCP performance metric collector daemon.
The syntax of the various formats of this
.B string
is described in
.BR PCPIntro (1)
where several examples are also presented.
.PP
The syntax allows the initial
.BR pmcd (1)
hostname to be optionally followed by a list of port numbers,
which will be tried in order when connecting to
.B pmcd
on that host.
The portlist is separated from the hostname using a colon, and
each port in the list is comma-separated.
.PP
In addition, one or more optional
.BR pmproxy (1)
hosts can be specified (currently, only one proxy host is supported
by the PCP protocols).
These are separated from each other and from the
.B pmcd
component using the @ character.
These may also be followed by an optional port list, using the
same comma-separated syntax as before.
.PP
.B __pmParseHostSpec
takes a null-terminated host specification
.B string
and returns an array of
.B pmHostSpec
structures, where the array has
.B count
entries.
.PP
These
.B pmHostSpec
structures that are returned via
.B hostsp
represent each individual host in the specification
.B string
and has the following
declaration:
.PP
.nf
.ft CW
    typedef struct {
        char    *name;       /* hostname (always valid) */
        int     *ports;      /* array of host port numbers */
        int     nports;      /* number of ports in host port array */
    } pmHostSpec;
.fi
.PP
.B __pmUnparseHostSpec
performs the inverse operation, creating a
.B string
representation from a number of
.B hosts
structures.
Where the
.B count
of structures indicated by
.B hosts
is greater than one, the proxy syntax is used to indicate a chain of
proxied hosts.
The size of the supplied
.B string
buffer must be provided by the caller using the
.B size
parameter.
.SH "RETURN VALUE"
If the given
.B string
is successfully parsed
.B __pmParseHostSpec
returns zero.
In this case the dynamic storage allocated by
.B __pmParseHostSpec
can be released by calling
.B __pmFreeHostSpec
using the address returned from
.B __pmParseHostSpec
via
.BR hosts .
.P
.B __pmParseHostSpec
returns
.B PM_ERR_GENERIC
and a dynamically allocated error message string in
.BR errmsg ,
if the given
.B string
does not parse, and the user-supplied
.B errmsg
pointer is non-null.
Be sure to
.BR free (3)
the error message string in this situation.
.PP
In the case of an error,
.B hosts
is undefined.
In the case of success,
.B errmsg
is undefined.
.PP
On success
.B __pmUnparseHostSpec
returns a positive value indicating the number of characters written
into the supplied buffer.
However, if the supplied buffer was too small, a negative status code of
.B \-E2BIG
is returned.
.SH SEE ALSO
.BR pmcd (1),
.BR pmproxy (1),
.BR pmchart (1),
.BR __pmParseHostAttrsSpec (3),
.BR PMAPI (3)
and
.BR pmNewContext (3).
